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PRELIMINARY
DS3 UNI FOR ATM
XRT7245
REV. 1.03
21
111
TxNEG
O
Transmit Negative Polarity Pulse:
The exact role of this output pin depends upon
whether the UNI is operating in the Unipolar or Bipolar Mode.
Unipolar Mode:
This output signal pulses “high” for one bit period, at the end of each
“outbound” DS3 frame. This output signal is at a logic “l(fā)ow” for all of the remaining bit-
periods of the “outbound” DS3 frames.
Bipolar Mode:
This output pin functions as one of the two dual-rail output signals that
commands the sequence of pulses to be driven on the line. TxPOS is the other output
pin. This input is typically connected to the TNDATA input of the external DS3 Line
Interface Unit IC. When this output is asserted, it will command the LIU to generate a
negative polarity pulse on the line.
112
TxLineClk
O
Transmit Line Interface Clock:
This clock signal is output to the Line Interface Unit,
along with the TxPOS and TxNEG signals. The purpose of this output clock signal is
to provide the LIU with timing information that it can use to generate the AMI pulses
and deliver them over the transmission medium to the Far-End Receiver. The user can
configure the source of this clock to be either the RxLineClk (from the Receiver portion
of the UNI) or the TxInClk input. The nominal frequency of this clock signal is 44.736 MHz.
113
VDD
***
Power Supply Pin
114
TxPOH
I
Transmit PLCP Frame POH Byte Insertion Serial Input:
This input pin becomes
active when the user asserts the TxPOHIns input pin. When this happens the user will
be permitted to serially input their own value for PLCP POH bytes into the “outbound”
PLCP frame. This data will be clocked into the UNI device via the TxPOHClk output
signal. This UNI will also assert the TxPOHMSB output pin when it expects the MSB
(Most significant bit) of the Z6 Byte (within the PLCP frame).
115
TxAISEn
I
Transmit AIS Pattern input:
When this input pin is set “high” the Transmit DS3
Framer will insert the AIS pattern into the DS3 output data stream.
116
TxPOHIns
I
Transmit PLCP Frame POH Data Insert Enable:
This input can be asserted to allow
the user to input his/her own value for the PLCP POH bytes via the TxPOH input pin,
in each PLCP frame, prior to transmission. If this input pin is not asserted, then the
UNI will generate its own PLCP POH bytes.
117
TxOHIns
I
Transmit DS3 Overhead Bits Serial Input Port Enable:
When the user wishes to
input his/her value for the overhead bits of the outbound DS3 data stream, he/she
should assert this input pin. When this pin is “high” then the TxOH Serial Input Port will
become active, and will begin sampling the TxOH input pin upon the rising edge of
TxOHClk signal. When this pin is low, then the TxOH Serial Input Port will be disabled,
and the overhead bits of the outbound DS3 data stream will be internally generated.
118
TxPOHClk
O
Transmit PLCP Frame POH Byte Insertion Clock:
This pin, along with the TxPOH
and the TxPOHMSB input pins, function as the “Transmit PLCP Frame POH Byte”
serial input port. This output pin functions as a clock output signal that is used to sam-
ple the user’s POH data at the TxPOH input pin. This output pin is always active, inde-
pendent of the state of the “TxPOHIns” pin.
119
TxOH
I
Transmit DS3 Framer Overhead Bits Serial Input Port input:
This pin, along with
the TxOHIns, TxOHMSB and TxOHClk pins comprise the “Transmit DS3 Framer OH
Bit” Serial Input Port. This input pin is active when the TxOHIns input pin is “high”; and
is disabled when TxOHIns is “l(fā)ow”. When this input pin is active, it will sample the
input signal on the rising edge of the TxOHClk signal. The data that is received via this
input will be inserted into the Overhead bits of the outbound DS3 Frame (via the
Transmit DS3 Framer Block)
120
TCellTxed
O
Transmit Cell Processor—Cell Transmitted Indicator:
This output pin pulses “high”
each time the Transmit Cell Processor transmits a cell to the Transmit PLCP Proces-
sor (or Transmit DS3 Framer).
PIN DESCRIPTION (CONT’D)
P
IN
N
O
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S
YMBOL
T
YPE
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ESCRIPTION